Re: [PATCH] drm/i915/gvt: Add __nonstring annotations for unterminated strings

[Kees Cook <kees@kernel.org>]

On Sun, Mar 23, 2025 at 12:42:41PM +0000, Damian Tometzki wrote:
> On Mon, 10. Mar 15:23, Kees Cook wrote:
> > When a character array without a terminating NUL character has a static
> > initializer, GCC 15's -Wunterminated-string-initialization will only
> > warn if the array lacks the "nonstring" attribute[1]. Mark the arrays
> > with __nonstring to and correctly identify the char array as "not a C
> > string" and thereby eliminate the warning.
> > 
> > Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117178 [1]
> > Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
> > Cc: Zhi Wang <zhi.wang.linux@gmail.com>
> > Cc: Jani Nikula <jani.nikula@linux.intel.com>
> > Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> > Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > Cc: Tvrtko Ursulin <tursulin@ursulin.net>
> > Cc: David Airlie <airlied@gmail.com>
> > Cc: Simona Vetter <simona@ffwll.ch>
> > Cc: intel-gvt-dev@lists.freedesktop.org
> > Cc: intel-gfx@lists.freedesktop.org
> > Cc: dri-devel@lists.freedesktop.org
> > Signed-off-by: Kees Cook <kees@kernel.org>
> > ---
> >  drivers/gpu/drm/i915/gvt/opregion.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/gvt/opregion.c b/drivers/gpu/drm/i915/gvt/opregion.c
> > index 509f9ccae3a9..f701638d3145 100644
> > --- a/drivers/gpu/drm/i915/gvt/opregion.c
> > +++ b/drivers/gpu/drm/i915/gvt/opregion.c
> > @@ -43,7 +43,7 @@
> >  #define DEVICE_TYPE_EFP4   0x10
> >  
> >  struct opregion_header {
> > -	u8 signature[16];
> > +	u8 signature[16] __nonstring;
> >  	u32 size;
> >  	u32 opregion_ver;
> >  	u8 bios_ver[32];
> > @@ -222,7 +222,7 @@ int intel_vgpu_init_opregion(struct intel_vgpu *vgpu)
> >  	u8 *buf;
> >  	struct opregion_header *header;
> >  	struct vbt v;
> > -	const char opregion_signature[16] = OPREGION_SIGNATURE;
> > +	const char opregion_signature[16] __nonstring = OPREGION_SIGNATURE;
> >  
> >  	gvt_dbg_core("init vgpu%d opregion\n", vgpu->id);
> >  	vgpu_opregion(vgpu)->va = (void *)__get_free_pages(GFP_KERNEL |
> > -- 
> > 2.34.1
> > 
> Hello together,
> 
> it doesnt resolve the build issue with gcc15 gcc (GCC) 15.0.1 20250228

This was a recent enhancement to GCC, and that 20250228 build does not
include it. (GCC 15 is not actually released yet...)

-- 
Kees Cook